1. Field of the Invention
The present invention relates to a data switching system having a plurality of data communication modules and applicable to the large-capacity data switching operation or the like.
2. Description of the Prior Art
In recent years there has been developed a private communication network for interconnecting various types of device such as computers, data terminals, personal computers, work stations, etc. These devices are distributed within a relatively limited area such as the same premises, the same building or the like. One example of such a network is proposed in U.S. Pat. No. 4,063,220 issued to Metcalfe et al. This network is composed of a single coaxial cable serving as a transmission path and a plurality of nodes, each of which has a transceiver and a controller. Since the transmission path is used in common, the transmission and reception of data can be achieved at every station connected thereto. The transmission speed in the network is generally as high as several 10 kilobits/second to 100 megabits/second which is far faster than that in a public communication network. Further, since each node can control the communication function of the network, the entire system cost is proportional to the number of the nodes. The respective nodes are of a passive type which do not necessitate the regeneration nor repeat of signals, because the system is constructed so that the signals are generally transmitted on the bus in both directions and an addressed node identifies only the signal addressed to itself during the period before the signal arrives at terminators located at both terminal end of the transmission path. Accordingly, even if any fault should arise at one node, the fault is confined only in that node so as not to affect other communications, so long as the node is a passive module.
Because of the use of a single transmission path in such a network, however, communication can be achieved at the same time only between two terminals. Therefore, if the bus network structure is kept intact, it is difficult to construct a large-scale switching system.